Analysis of the Dielectric Breakdown Characteristics for a 252-kV Gas Circuit Breaker

Abstract

A study was carried out on the characteristics of the dielectric strength of gaseous working medium in a puffer circuit breaker following current interruption. A reduced critical electric field strength ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> was defined. Its value for SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas within the temperature range of 300 to 3000 K and pressure range of 1 to 32 atm was obtained by solving the Boltzmann equation with most recent atomic data, which allows the determination of the critical electric field strength <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> at different temperature and pressure. The dielectric behavioral pattern of the breaker was then characterized by applying the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> data to the temperature and pressure fields obtained by a 2-D magneto-hydro- dynamics model encompassing all important mechanisms operating in the arcing process. The <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> distribution at 80 and 110 μs after current zero was then compared to the electric-field distribution to arrive at important information regarding the weakest point or regions in the design. Using a standard rate of rise of recovery voltage profile, the critical dielectric withstand level of the breaker was also predicted.